This paper presents an analysis of the merits of the original Yarbus experiment on eye movements with respect to judgments on differences in cognitive layer processes. The principles thus derived are applied to the development of an equivalent auditory experiment where, instead of eye movements, the response of the subject is observed by EEG measurements. Results from a preliminary trial are also included in which EEG analysis is used to ascertain the attended sound source in a multiple sound source environment. The investigation is part of ongoing research to improve the usefulness of hearing instruments and is also relevant in relation to other scientific investigations concerning the processing of sounds in complex acoustical environments by the human brain.